This invention relates to an alarm watch which is able to rapidly recover its alarm sounding capability often water enters into the sound releasing cavity of the watch.
An alarm watch has a electro-acoustic transducer. In the alarm watch, sound releasing holes are formed through a portion of the casing at locations opposite the vibrating plate of the transducer or through a cover fitted on the casing so that the vibrating sound of the vibrating plate is efficiently released to the exterior of the watch casing.
During use of an alarm watch, water occasionally enters into the sound releasing cavity containing the vibrating plate and the sound releasing holes, for some reason or other. When water enters into the sound releasing cavity and adheres to the surface of the vibrating plate, the equivalent mass of the vibrating plate itself varies and as a result, the resonance frequency of the vibrating plate, the sound volume and the sound tone color also vary.
On the other hand, the area of the openings for emitting the audible sound becomes smaller when water adheres on the surface of the sound releasing holes and the volume of the sound releasing cavity becomes smaller when water adheres on other surfaces of the sound releasing cavity and under such conditions the sound tone color and the sound volume vary accordingly. In the conventional type alarm watch, if water enters into the sound releasing cavity, it is not apt to escape for quite some time so that much time elapses before the alarm sounding function recovers to its former condition.